Key-plunger unit.



E. B. CRAFT.

KEY PLUNGER UNIT.

APPLIOATION FILED sEPT.2, 1911.

Patented June 16,1914.

W/f/vessesx Affy COLUMBIA PLANOGRAPH co., WASHINGTON, D. c.

UNITED STATES PATENT OFFICE.

EDWARD B. CRAFT, OF HACKENSACK, NEW JERSEY, ASSIGNOR T0 WESTERN ELECTRIC COMPANY, OF NEW YORK, N. Y., A CORPORATION OF ILLINOIS.

KEY-PLUNGER UNIT.

Specification of Letters Patent.

Patented June 16, 1914.

To all whom it may concern:

Be it known that I, EDWARD B. CRAFT, citizen of the United States, residing at Hackensack, in the county of Bergen and State of New Jersey, have invented a certain new and useful Improvement in Key- Plunger Units, of which the following is a full, clear, concise, and exact description.

This invention relates to switch key structures and has for its objectst-he provision of a plunger unit in which each group of switch springs and its cooperating plungers are associated in a unit structure which may be removed from the supporting base without disturbing any of the other groups of springs or their associated parts.

According to this invention each group of springs is mounted in a U-shaped frame member of suitable material which also supports the plunger in proper relation to the springs by means of a bridge piece adapted to be held between the frame members by the clamping thereto of the springpile.

In the drawings-Figure 1 is a view in side elevation with parts in section of a switch key embodying my invention. Fig. 2 is an end elevation of the parts shown in Fig. 1. Fig. 3 is a detail view'of the plunger.

part-s before assembly.

Referring first to the key base in connection with which the plunger unit of thisinvention may be used, 5 designates a channel member carrying a top or face plate f hard rubber or other suitable material and having at each end a depending stud 7 by,

means of which said base is secured to a key shelf. Only one of the studs 7 for fastening the base to the key shelf is shown as the base and fastening means thereof form no part of this invention. The channel piece 5 is adapted to support a U-shaped frame member comprising legs 8, 8 and a cross or connecting piece 9. This U-shaped member is preferably formed of a single strip of metal bent or stamped in to the required shape and having sufficient resilience to permit the free ends of the legs 8, 8 to be sprung laterally without bending or distorting said legs. Springs 12, 12 are secured between the legs 8, 8 of the U-shaped frame member near the open end thereof by means of screws 13, 13 passing through one of said legs and openings in said springs 12, 12 and engaging screw threaded apertures in the other of said legs. Two of the springs 12, 12 are provided at their uppcrends with outwardly flared portions 15, 15 adapted to be engaged by a plunger button 16 carried upon the lower cnd'ofia plunger rod- 17. As shown, the plunger rod 17 is provided on its lower end with a screw-threaded portion 18 adapted to engage interior-threads in said button 16. Adjacent to this screw-threaded portion is a reduced portion 19 which is provided on its lower end andupon opposite sides thereof with cut-away or flattened portions 20, 20, this flattened portion being adapted when the unit is'assembled to pass through an oblong or corresponding shaped opening 21 in a bridge piece 22 to prevent said plunger rod turning. The upper end of said plunger rod 17 passes through alined openings in the connecting piece 9 of the U-shaped member, the channel member and the rubber facing plate and is provided upon its outer end with a screw-threaded portion 23 adapt ed to receivea cap 24.. The bridge piece 22 is provided at its ends with projections 25, 25 adapted to engage openings 26, 26 in the legs 8, 8 and is clamped therebetween when the unit is assembled. This bridge not only forms a guide for the key plunger which prevents it turning or twisting out of alinement with the engaging portions of the springs 12, 12, but adds rigidity to the structure as a whole. Furthermore, such a structure avoids the use of screws or rivetng, thus making the device one easy of assembly and sure in its operation.

Surrounding the reduced portion 19 of the plunger rod 17 is a spiral spring 30, the

lower end of which bears against the upper face of the bridge piece 22, the upper end being in engagement with a washer 31 bearing against a shoulder 32 at the upper end of said reduced portion 19. Surrounding said spring 30 and resting upon the upper face of said bridge 22 is a sleeve 33 adapted I to be engaged by said washer 31 in the operation of the key plunger 17 to limit the downward movement thereof.

The connecting piece 9 of the U-shaped member is provided with screw-threaded.

openings 35, 35 adapted to receive screws 36,

36 for securing the plunger unit to the channel 5 of the base.

The advantages of such a structure are apparent inasmuch as it is readily seen that the unit may be assembled entire with the exception of placing the key cap thereon before it is applied to the base, thus enabling all springs and other parts to be easily'adjusted without interfering with. any of the other units of the key. Moreover, in case it is desired to make repairs of a key made up of these units, it can be readily done by simply replacing the unit without having to remove the entire key and thus disturbing the wiring of several lines or circuits instead of only one.- Furthermore the units equipped with springs arranged for various combinations of circuits may be carried by the users of the keys or manufacturer and given a code number bywhich they may be readily supplied.

I claim:

1. In a switch key, the combination with a channel formed base, of a frame member having outwardly extending parallel legs secured in saidchannel, switch. springs mounted between said legs at the outer ends thereof, a plunger for ope-rating said springs, and a bridge piece through which said plunger passes secured between said legs adjacent to the inner ends thereof.

2.1n a switch key, the combination with a key' base, of a U-shaped frame member adapted to be attached thereto, switch springs supported between the legs of said U-shaped frame member, a plunger button for operating said springs, a plunger rod carrying said button, and a bridge piece mounted between the legs of said U-shaped frame a member through which one end of said plunger rod passes, the other end of said plunger rod passing through said frame member.

3. In a switch key, the combination with a key base, of a U-shaped frame member adapted to be attached thereto, switch springs supported between the legs of said U-shaped frame member, a plunger button, a plunger rod carrying said butt-on, said plunger being provided near one end with a flattened portion, a bridge piece mounted between the legs of said frame member and having an oblong opening of the same contouras the flattened portion of said plunger rod and through which said flattened portion ofsaid plunger rod passes, the other end of said plunger rod passing through an opening in said U-shaped frame member.

4. In a switch key, the combination with switch springs, of ,a U-shaped frame member between the legs of which said springs are secured, each of said legs being provided adjacent the inner ends of said springs with an aperture, a bridge piece having projections thereon adapted to engage said apertures and a plunger supported by said bridge piece and the connecting piece of said U-shaped frame member.

5. T he combination with a U- shaped frame member, of switch springs supported between the legs thereof, a bridge piece supported between said legs adjacent to the in ner ends of said springs, a plunger button for operating said springs, a plunger rod for said button having one end passing through said bridge piece and the other end passing through said frame member, said plunger rod having a shoulder thereon, a coiled spring surrounding said plunger rod and bearing-at one end against one face of said bridge, a washer adapted to engage said shoulder and against which the opposite end of said spring bears, and a sleeve surrounding said spring adapted to limit the downward movement of said plunger.

In .witness whereof, I hereunto subscribe my name this 1st day of September A. D.,

EDWARD B. CRAFT. Witnesses IRVING IVIAODONALD, MORGAN VVAsHBURN, Jr.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents. Washington, D. G. 

